**Core Concept**
Edward Jenner is credited with the development of the smallpox vaccine, but the term "father of public health" is often attributed to John Snow, a British physician who played a crucial role in the prevention of cholera outbreaks. Snow's work on the Broad Street pump in London led to the removal of the handle, stopping the spread of cholera in 1854.

**Why the Correct Answer is Right**
John Snow's work on the cholera outbreak in London in 1854 is considered a landmark moment in the history of public health. He used epidemiological techniques, including mapping and data analysis, to identify the source of the outbreak as the contaminated water from the Broad Street pump. Snow's findings led to the removal of the pump handle, which stopped the spread of cholera in the area. His work demonstrated the importance of sanitation and clean water in preventing the spread of infectious diseases.

**Why Each Wrong Option is Incorrect**
**Option A:** Edward Jenner is the father of immunology, credited with developing the smallpox vaccine, but not the father of public health.
**Option B:** Louis Pasteur made significant contributions to vaccination and germ theory, but is not typically referred to as the father of public health.
**Option C:** Florence Nightingale is considered the founder of modern nursing, but not the father of public health.

**Clinical Pearl / High-Yield Fact**
John Snow's work on the Broad Street pump highlights the importance of epidemiological techniques, including mapping and data analysis, in preventing the spread of infectious diseases.

**Correct Answer: D. John Snow.**